(1) Field of the Invention
This invention relates to a drive apparatus comprising an engine, a main clutch and a power shift transmission.
(2) Description of the Prior Art
Referring to FIG. 6, a drive apparatus according to the prior art has a main clutch 2 interposed between an engine E and a power shift transmission 1. This construction has a problem of requiring a change speed power shift means 13 having a great shifting force, which results in the shift means 13 per se being large size, and the power shift transmission 1 and a hydraulic change speed mechanism therefore having to be large size too.
More particularly, in effecting a change speed operation with the prior art construction after the main clutch 2 and the shift means 13 are put out, one of freely rotatable driven gears Gb is rigidly connected by operating the shift means 13 to a driven shaft S2 rotating at a different speed by inertia to the driven gear Gb. At this time the shift means 13 has to be operated against mass inertia of all of an input shaft S1, a plurality of drive gears Ga fixedly mounted thereon, and the driven gear Gb in constant mesh with the drive gears Ga, respectively, and therefore the shift means 13 needs a great shifting force.